The subject matter disclosed herein relates generally to imaging systems, and more particularly, embodiments relate to systems and methods for acquiring photon count information using detectors of the imaging systems.
Conventional imaging systems, such as a Computed Tomography (CT) imaging system, are used to scan an object of interest to acquire image information. Typically, the imaging systems include an X-ray source that is configured to emit X-rays toward the object. A detecting device, such as an array of radiation detectors, is positioned on the other side of the object to detect the X-rays transmitted through the object.
CT imaging systems may acquire the imaging information by operating in a current mode. When operating in the current mode, the detector converts radiographic energy into current signals that are integrated over a time period, then measured and ultimately digitized. A drawback of such detectors however is their inability to provide data or feedback as to the number and/or energy of photons detected. Accordingly, CT imaging systems are also configured to operate in a photon-counting mode. While operating in the photon-counting mode, some CT imaging systems may not be able to count x-rays at x-ray photon flux rates typically encountered with conventional CT systems. For example, the count-rate capability of a solid-state detector, such as a Cadmium Zinc Telluride (CZT) detector or a Cadmium Telluride (CdTe) detector, operating in the photon-counting mode, is limited by the pulse shaping capability of the detector scintillators. For example, the maximum photon count-rate for a conventional CZT detector is limited to approximately 1/eT per electronics channel, where T is the dead time. Dead time occurs when a photon impacts a detector crystal and the detector is busy processing or counting the photon.
Accordingly, when some CT imaging systems are operating in the photon-counting mode, detector saturation, or detector pile-up, may occur. Pile-up also affects light curves, suppressing high-count rates. In other words, these detectors typically saturate at relatively low X-ray flux level thresholds. Above these thresholds, the detector response is not predictable or has degraded dose utilization. That is, once a pixel is saturated (corresponding to a bright spot in the generated signal), additional radiation will not produce useful detail in the image.